From the NAMBA rulebook:
Tunnel hulls will be of a tunnel configuration with no restriction as to size, weight, or
type of construction. A hull will be classified as a tunnel if it meets the following
requirements:
a. The general design of the tunnel hull should follow as closely as possible to
the design of the full sized OPC tunnel hulls.
b. The hulls will be stand-off scale, with no restrictions as to canted sponsons,
tunnel dihedral, air traps, strakes, stern stabilizing fins, etc.
c. Imaginative painting, striping, company logos, and lettering schemes may be
added and are encouraged.
d. A close to scale driver with at least the head and shoulders must be provided
unless proof of a reclining driver is offered as in OPC hulls. Boats without
drivers must be painted to include a darkened windshield to resemble a
closed-in cowl appearance.
e. The tunnel may be of any design, width, or depth, but must run the full length
of the hull.
f. The tunnel must connect two outer hulls or sponsons which are unbroken and
must also run the full length of the hull. Picklefork designs are acceptable.
Outrigger configurations are not acceptable.
g. Sponsons may be of any design and may include stepped surfaces on the
wetted running sponson bottom of not more than 1/8" in depth. The 1/8" steps
may not be less than 5" apart if used across the sponson. Only one step may be
used if used lengthwise on the sponson.
h. No hull will be allowed to have a recessed or picklefork bow which exceeds
30 percent of the overall boat length. Airslots in the center hull must be
subtracted from the overall hull length.
From part b I would assume small wings are allowed. I've seen tunnels raced with both front wings between the sponsons and rear wings over the center section. These pictures of Rod Geraghty's tunnel shows an innovative design that I'm sure could qualify anywhere.
Lohring Miller
Geraghty 3.5 tunnel.JPG
Geraghty 3.5 tunnel1.JPG